18.4 Leukocytes and Platelets

what are leukocytes

WBCs known for the bodys defense against disease

what is the main function of leukocytes

protect body against invading microorganisms and famaged cells

what role do platelets play in body

help repair damaged blood vessels and provide growth factors for healing

what else do leukocytes do

clean debris

what is the main difference between leukocytes and erythrocytes in terms of their numbers

leukocytes are far less numerous

how many leukocytes are there in liters

5000 - 10,000 per microliter

what are the characteristic of leukocytes

less numerous, larger, many types, short lifespan, and distinctive movement

why are wbcs largers

bc only formed element of complete cells with a nucleus and organelles

how long do wbcs live

few hours or few mintues in the case of acute infection

what is a ditinctive characteristic of wbcs

their movement, they can leave the bloodstream to perform their defensive dunction in tissues

the bloodstream is like what for wbcs

a highway they travel and exit to their destination

when wbcs arrive at their destination, they are given names such as

macrophage or microglia dependinf on their function

what is emigration

(diapedesis) process of wbcs squeeze through adjacent cells in blood vessels to enter tissues

what is another word for emigration

diapedesis

once wbcs exit the bloodstream or capilarries, where do they go

lyphatic tissue, bone marrow, spleen, thymus, or other organs

where else might wbcs move towards

the direction in which they are drawn by chemical signals

what does positive chemotaxis mean

movement in response to chemicals

what is the positvie chemotaxis in term of leukocytes being oresent

movement of wbcs moving towards chemical signals emitted by injured or infected cells calling more wbcs on site

how are wbcs clasified

based on the presence or absence of visible ganules in their cytoplasm

what are granular leukocytes

wbcs that contain abudnacnt granules within the cytoplasm

what are the 3 granular lekocytes

neutrophils, eosinophils, and basophils

what are agranular leukocytes

wbcs that have fewer and less obvious granules

what are the 2 agranular leukocytes

monocytes and lymphocytes

what happens to monocytes after they mature

mature into macrophages which are phagocytic

where do lymphocytes arise from

lymphoid stem cell line

what are the characteristics of granular leukocytes

short lifespan, lobed nucleus, classified according to type of stain that highlights their granules

what is a neutrophil

type of granular leukoctye with small granules that stain light lilac and a nucleus with two to five lobes

what do neutrophils do

rapid responder to infection and is efficient phagocyte with a preference for bateria

what is the significance of the lobed nucleus in neutrophils

older neutrophils have increasing numbers of lobes and are often referred to as polymorphonuclear

what is polymorphonuclear

nuclues with many forms, typically referring to older neutrophils with multiple lobes

what are bands

younger and immature neutrophils that begin to develop lobes

what are some of the contents of neutrophil granules

lysozyme and defensins

what is a lysozyme

an enzyme capable of lysing, or breaking down, bacterial cell walls;

what is an example of lysozyme

oxidants such as hydrogen peroxide;

what are defensins

proteins that bind to puncture bacterial and fungal plasma membranes, causing cell contents to leak out

what do abnormally high counts of neutrophils indicate

high counts indicate infection or inflammation

what do abnormally low counts of neutrophils indicate

drug toxicity and increase susceptibility (vulnerabiluty) to infection

what percentage of total leukocyte count do eosinophils typically present

2-4 %

what is distinctive about the granules of eosinophils

stain best with an acid stain known as eosin and have a distinct red to organge color

how many lobes of eosinophil nucleus have

3 lobes

what is the function of the granules in eosinophils

they contain antihistamine molecules that counteract histamines and molecules toxic to parasitic worms

what are histamines

inflammatory chemicals produced by basophils and mast cells

how can parasitc worms enter the body

through the integument or by consuming raw or undercooked fish or meat

what are eosinophils particulary effective at doing

phagocytosis, esp when anitbodies bind to the target and form an antigen-antibody complex

what do high counts of eosinophils indicate

allergies, parasitic worm infestations, and some autoimmune disease

what do low counts of eosinophils indicate

drug toxicity and stress

what percentage of total leukocyte count do basophils typically represent

less than 1 percent

what is distinctive about the granules of basophils

they stain best with basic (alkaline) stains and pick up a dark blue stain

what do granules of basophils release

histamines

what do histamines contribute to in basophils

inflammation, heparin, which opposes blood clotting

how many lobes of nucleus do basophils have

2 lobed but difficult to see bc of dark blue stain

what do basophols do

intensify inflammatory response

what trait do basophils share the intensify inflammatory response with

mast cells

what do high counts of basophils indicate

allergies, parasitic infections, and hypothyroidism

what do low counts of basophils indicate

pregnancy, stress, and hyperthryoidism

what is the least common granular wbc

basophils

what is distinctive abt the granules in argranular leukocyte

smaller and less visible than granular leukocytw

what is the shape of the nucleus in agranular leukocyte

simple, sometimes with an indentation but without distinct lobes

what are the two major types of agranular leukocytes

lymphocytes and monocytes

where do lymphocytes originate from

lymphoid stem cells

lymphocytes are the only?

formed element of blood that arises from lyphhoid stem cells

where do lymphocytes develop and reproduce after initial formation in bone marrow

lymphatic tissue

what is the 2nd most common type of leukocyte

lymphocytes

what percentage of leukocytes are lymphocytes

about 20-30%

what is the role of lymphocytes in the body

essential for immune response

what are the characteristics of large lymphocytes

10-14 micrometer with smaller nucleus to cytoplasm ratio and more granules

what is the characteristics of small lymphocytes

6-9 micrometers with larger nucleus to cytoplasm ratio

what are the 3 major groups of lymphocytes

natural killer (NK) cells, B cells, and T cells

what are natural killer (NK) cells

type of lymphocyte that plays a role in the immune system and don’t need prior exposure to pathogens to recognize and attack affected cells or tumor cells

what is the function of natural killer (nk) cells

recognize and target cells that do not express “self” proteins or contain foreign or abnormal markers

what types of cells do NK cells target

cancer cells, cells infected with a virus, and other cells with atypical surface proteins

what type of immunity do NK cells provide

generalized, nonspecific immunity

which type of lymphocytes are typically larger

NK cells

what are B cells also called

B lymphocytes

what are T cells also called

T lymphocytes

what is the role B lymphocytes and T lymphocytes in the immune system

defend the body against specific pathogens and are involved in specific immunity

what is one form of B cells

plasma cells

what do plasma cells produce

antibodies or immunoglobulins that bind to specific foreign or abnormal components of plasma membranes

what type of immunity do B cells provide

humoral (body fluid) immunity

what is the role of T cells in the imune system

provude cellular level immunity by physically attacking foreign or diseased cells

what are memory cells

type of B or T lymphocyte that forms after exposure to a pathogen

what is the function of memory cells

mount rapid responses upon subsequent exposures

how long do memory cells live for

years

where do b cells underog maturation

in Bone marrow

where do t cells undergo maturation

in Thymus

abnormally high lymphocyte counts indicate

viral infections and some type of cancer

abnormally low lymphocyte indicate

prolonged chronic illness, immunosuppression, HIV infection, drug therapies that often involve steroids

what is the origin of monocytes

myeloid stem cells

what percentage of total leukocyte count do monocytes represent

2-8%

what are the characteristics of monocytes

large, 12-20 micrometers with indented or horseshoe shaped nuclei

what are monoytes

type of agranular leukocyte that matures into macrophages, which phagocytize debris, foreign pathogens, and damaged cells

what are macrophages

monocytes that left the circulation

what is the role of macrophages

phagocytize debris, foreign pathogens, damaged cells, and release antimicrobial defensins and chemotactic chemicals

abnormally high count of monocyte indicates

viral or fungal infections, tuberculosis, and some forms of leukemia

abnormally low count of monocytes indicate

bone marrow suppression

what is the typical lifespan of most leukocytes

short, hours or days

where does production of wbcs behin

bone marrow

what influences production of wbs in bone marrow

colony stimulating factors (CSFs) and interleukins

where does 2ndary prod. and maturation of lymphocytes occur

lymphatic tissue known as germinal centers

what is unique about lymphocytes ability to produce clones of cells

can produce clones of cells with identical properties through mitosis, enabling long term immunity to previously encountered threats